Network Switches

I use fiber conversion but only to air-gap my cable modem from my router.  This is mostly to deny lightning this path to all my expensive electronics in the house.  It comes at a cost however in that I now have 2 additional power supplies to deal with.  In the data closet that’s fine, but I would only use this at the audio side if my streamer took fiber directly.  Otherwise I’m just creating more problems than necessary. 

For Ethernet isolation, again, my biggest concern is lightning. The twisted pair strands in the Ethernet cable are inherently galvanically isolated.  They have to be or you’d have high currents running from switch to switch in some buildings.  However at the end of long runs (30' or so) I use medical grade Ethernet isolators (UL 60-601) instead of audio grade.  The reason is medical-grade isolators are tested for 4kV isolation and can deny a voltage surge another path.   Avoid any network surge protector with a ground wire.  

My advice is that switches upstream don't matter.  Bad power supplies do.  

Keep your networking power supplies (i.e. wall warts) off your clean power area.  Use a separate conditioner if you need to, and consider using iFi power supplies for them if they are near your audio. 

Also use shielded IC's and power cords (the cheap shielded, not the expensive shielded) to avoid noise pickup.  I like to make my own from parts at Parts Connexion.